Microsoft lets Azure Linux 4 out of the cloud in downloadable ISO form

os platforms

Fedora-derived server distro is ready for local testing, but production deployments should wait

Microsoft's Fedora-derived Azure Linux 4 has hit a new milestone: you can now run it outside of Azure. The project's GitHub page now offers ISO file downloads in addition to its Azure Marketplace page.

We covered the Azure Linux 4 announcement in May, and it is still in preview. You should not deploy this in production just yet. The availability of ISO files for installation in a local VM is a welcome step forward, though. They are not where you might expect to find them for a FOSS project on GitHub, under Releases – there are just some kernel builds there. You need to scroll down to the section headed Using Azure Linux and then expand the section headed ISO Installer. Both x86-64 and Arm64 images are available.

Azure Linux 4 is the successor to the older Microsoft CBL-Mariner distro we looked at in 2022, which in 2024 transformed into Azure Linux 3. Now, configuration is mostly in TOML files, while older releases used .spec files inherited from VMware Photon OS, which was mentioned on The Register a decade ago.

This build, which reports its name as "Four Beta," uses kernel 6.18 and systemd 258.4. It derives most of its package sources and packaging metadata from Fedora, but that does not mean this is a rebadged edition of Fedora Server, and you should not expect it to be compatible with Fedora packages. Only two repositories are configured by default: azurelinux-base and azurelinux-microsoft, both on packages.microsoft.com/azurelinux/. There isn't a great deal in them yet, or in the distro itself: for instance, we were surprised to find the less command missing, and htop was not available to install.

The good news is that you do get the dnf package manager command, though. Azure Linux 4 is not some immutable dedicated container host. This is because Microsoft has one of those too – Azure Container Linux – which is intended to serve as a container host for the Azure Kubernetes Service, and it's on GitHub.

So don't expect to find GNOME or any other nice graphical desktop in Azure Linux 4: this is a distro intended to run in an Azure VM, although it works fine inside a local Hyper-V VM. The preview is only a 1 GB download, and takes 1.1 GB of disk and 359 MB of RAM. The installation program is a very basic command-line tool, and, by default, it creates and installs into an LVM config, with memory ballooning enabled.

All this highlights that this is not some general-purpose PC OS, intended to replace Windows, or Windows Server, or anything of the kind. This is not the "Microsoft Linux" that was parodied at the turn of the century (although we do like the "Gates Private License, which means you can freely use this Software on a single machine without warranty after having paid the purchase price and annual renewal fees").

Azure Linux 4 isn't really meant for humans to install at all, let alone on bare metal. Its typical role would be to be automatically provisioned by some deployment pipeline. The ISO file is just for testing purposes. There are some reports of a two-year update cycle, but the published lifecycle doesn't mention that, only that it will use LTS kernels and get monthly security updates.

Azure Linux 4 reflects that Microsoft is bringing some more of its toolchain in-house. Two years ago, we reported that it moved LinkedIn to Azure Linux, thus removing a dependency on an external product that was end of life: the CentOS Linux distribution, replaced by the rather different CentOS Stream. Now, with the move to Fedora as its upstream source, it's removing another dependency on the aging VMware Photon OS. As The Reg has reported recently, other VMware customers are moving away from Broadcom, including international supermarket chain Tesco and telco giant T-Mobile. ®